Combustion chamber for gas dynamic laser

ABSTRACT

A combustion chamber for use with a nozzle in a gas dynamic laser to produce a proper specie in a lasing region downstream of said nozzle is formed having two radial injection planes spaced axially apart. At the first plane an oxidant is injected through a plurality of holes located circumferentially around the chamber with a fuel being injected by nozzles located concentrically within said holes. Oxygen and nitrogen, a diluent, are injected at the second radial plane. Means for injecting additional oxygen into the oxidant is provided at the first plane. In one modification, the oxidant is shown as O2 with N2 added while the fuel is the combination of CO and H2. O2 and N2 also are injected at the second plane. In another modification, the oxidant injected at the first plane is also O2 with N2 added while the fuel is CO and H2 with only N2 being injected at the second plane. An ignition means is shown with both modifications. The combustion system burns CO and H2 and O2 and dilutes with N2 in two stages. A mixing chamber extends downstream of said second plane.

United States Patent [191 Chamberlain Dec. 18, 1973 COMBUSTION CHAMBER FOR GAS 2,707,373 5 1955 Maynor 60/3969 DYNAMIC LASER Primary Examiner-Samuel Feinberg l t h be 1 [75] nven or .gzlllclhC Ft}? r am, North Palm Atmmey Jack N McCarthy [73] Assignee: United Aircraft Corporation, East [57] ABSTRACT Hartford, Conn. A combustion chamber for use with a nozzle in a gas 1 Flledl 30, 1970 dynamic laser to produce a proper specie in a lasing Appl. No.: 73,624

[63] Continuation of Ser. No. 733,220, May 24, 1968,

abandoned.

[52] U.S. Cl 431/351, 60/3946, 60/3965 [51] Int. Cl. F23t1 15/00 [58] Field of Search..... 331/945 G; 431/96,

[56] References Cited UNITED STATES PATENTS 2,457,157 12/1948 King, Jr. 60/3965 2,837,893 6/1958 Schirmer 60/3965 2,967,393 1/1961 Von Braun 60/230 2,926,495 3/1960 Benson et al.. 60/3967 2,930,192 3/1960 Johnson 60/3965 3,306,333 2/1967 Mock 60/3965 2,575,070 11/1951 Reed et al... 60/3965 2,655,786 10/1953 Carr 60/206 region downstream of said nozzle is formed having two radial injection planes spaced axially apart. At the first plane an oxidant is injected through a plurality of holes located circumferentially around the chamber with a fuel being injected by nozzles located concentrically within said holes. Oxygen and nitrogen, a diluent, are injected at the second radial plane. Means for injecting additional oxygen into the oxidant is provided at the first plane. In one modification, the oxidant is shown as 0 with N added while the fuel is the combination of CO and H 0 and N also are injected at the second plane. In another modification, the oxidant injected at the first plane is also 0 with N added while the fuel is CO and H with only N being injected at the second plane. An ignition means is shown with both modifications. The combustion system burns CO and H and O and dilutes with N 2 in two stages. A mixing chamber extends downstream of said second plane.

8 Claims, 2 Drawing Figures COMBUSTION CHAMBER FOR GAS DYNAMIC LASER This application is a continuation of Ser. No. 733,220 filed May 24, 1968, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a combustion chamber, and especially to one for use with a gas dynamic laser to produce an exhaust molecular mass fraction which can be used in a laser cavity to initiate or amplify a laser beam.

SUMMARY OF THE INVENTION In the combustion means disclosed, means have been provided to stably burn gaseous fuel and oxidants which are ordinarily hard to burn. Further, this type burner will also stably burn very lean or rich fueloxidant mixture ratios which are usually hard to burn.

A combustion system is provided having two stages of injection for fuels, oxidants and diluent. It is also a feature of this invention to have fuel injected concentrically within a first stage of oxidant holes to provide thorough mixing and achieve a relatively uniform fueloxidant mixture throughout the front end of the combustor. The mixture ratio is chosen so as to provide best burning. The concentric fuel-oxidant holes inject their fluids substantially radially inwardly to minimize both turbulence and velocity in the front end.

A further feature of this invention is to dilute the burning mixture to the desired temperature and composition by adding excess oxidant or diluent.

Oxygen may be injected adjacent the front end of the burner to improve burning if very hard-to-burn mixtures are used.

A feature to damp out high frequency instabilities may be provided, such as a perforated liner, if these conditions are encountered.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view taken along the length of a' combustor incorporating the invention.

FIG. 2 is 'a similar view of a modification of the combustor.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a combustion chamber 2 is shown having an outer casing 4 with a inner perforated liner 6 positioned therein by a plurality of posts 8. The downstream end of said combustion chamber is connected to the input of a nozzle 9. An oxidant is directed into said combustion chamber at two locations A and B along the length of said combustion chamber. An oxidant tank 10 is connected to a manifold 12 by a conduit means 14 having a control valve 16, therein controlling the flow of oxidant to the manifold. The manifold 12 is connected to a plurality of openings 18 in the side of the combusion chamber 2 by individual conduit sections 20. These openings 18 appear at location A and are in a plane perpendicular to the axis of said combustion chamber. The tank 10 also has a conduit means 24 connecting it to a manifold 22; a control valve 26 is located in this conduit means. Manifold 22 is connected to a plurality of openings 28 in the side of the combustion chamber 2 by individual conduit sections 30. These openings 28 appear at location B, downstream of location A, and are in a plane perpendicular to the axis of said combustion chamber.

Fuel is injected into said combustion chamber by injectors 40. A plurality of these injectors 40 extend inwardly from a manifold 42 and each individual injector 40 extends into one conduit section 20 and has its free end located in the center of each opening 18 and on the same plane therewith. The fuel system comprises two tanks 44 and 48. These two tanks are connected by conduits 47 and 49, respectively, to a conduit 51 which is in turn connected to the manifold 42. A control valve 53 is located in conduit 46, a control valve 55 is located in conduit 50, and a control valve 57 is located in conduit 51. Each of the valves 53 and 55 controls the amount of its own specific fluid carried by its associated tank. Valve 57 controls the total amount of flow to the manifold 42.

Oxygen is injected into at least three of the conduit sections 20 through pipe sections 60 through a manifold 62. Oxygen is fed to the manifold from an oxygen supply tank 64 through conduit means 66 which has a control valve 68 therein. Means 70 is connected to a device 72 for producing an ignition means for the combustion chamber.

Referring to FIG. 2, while several of the parts are the same as shown in FIG. 1, there are some changes which will be set forth below.

Conduit sections 30a and 20a now extend from a manifold 22a which is connected by a conduit 24a to a tank 10a. A control valve 26a is located in conduit 24a. The individual injectors 40a extend from tanks 44a and 48a exactly as in FIG. 1. Part of the oxygen is injected at location A as before. The remainder of the oxygen is injected into the forward end of the combustion chamber at C through conduit means which is controlled by valve 78. A torch igniter 79 is used to provide ignition in this figure and is of the type which uses hydrogen and oxygen as fuel and oxidant. The igniter has oxygen directed thereto by a conduit 81 having a control valve 82 from tank 64a. Hydrogen is directed to the igniter from tank 48a through conduit 84. A control valve 86 is located in conduit 84.

In constructing a burner of this type the concentric fuel-oxygen holes should be located at a distance of over one-half of the combustion chamber diameter downstream of the front end. In one chamber successfully tested, the distance between the front of the combustion chamber and the first stage of holes was made equal to the diameter of the inside of the casing 4. The second stage of holes should be placed roughly one diameter or more downstream from the first stage. In the burner construction referred to above, this distance was made equal to the diameter of the inside of casing 4. The mixture and temperature of the exhaust leaving the second stage will be uniform at the end of the mixing chamber 90 or 90a at a distance approximately equal to two times the diameter of the casing. This will insure that a gas having the proper characteristics for being expanded in a nozzle 9 and providing a proper specie on the other side for use in the lasing region 11 of a gas dynamic laser.

In both modifications, it has been made possible to add extra oxygen to the combustion chamber between the front end of the chamber and the first stage of openings. The use of extra 0 can be increased during starting to provide certain ignition and steady burning capability at atmospheric pressure start. As the system warms up and pressure is increased, the need for high percentage of will fall off and the extra supply can be reduced.

In the successfully tested combustor, the holes 18 were made with an inner diameter of approximately 2 inches, as mentioned herein before, there were 6 of these around the chamber. Each injector 40 was formed with an inner diameter of approximately 0.6 inches and an outer diameter of over 1 inch. The outer dimension of the injector 40 is to be kept as accurate as possible when it is a portion located within a conduit section 20. This makes the oxidant entry holes actually an annular opening having a width (r r,) equal to one-half inch. The manifold 42 had an inner diameter of 1% inch. The distance of the straight portion of the conduit section 20 connected to the casing 4 extended for at least 4 inches. This is to provide for equalizing the flow through the annular opening for injection of the oxygen. The inner diameter of the holes 28 was made approximately 2 inches.

It is to be understood that the invention is not limited to the specific description above or specific figures shown, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward end closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means f0r supplying a diluent from said diluent supply tank to said third conduit means; said combustion chamber is formed circular in cross-section and said first predetermined distance is approximately equal to the diameter of said combustion chamber.

2. A combustor for a gas dynamic laser as set forth in claim 1 wherein the first set of opening means includes a plurality of first openings with a conduit having a smaller opening located concentrically in said first opening each conduit forming an annular opening with its cooperating first opening, each first opening and smaller opening of said conduits being directed to inject the fluids substantially radially inwardly along said first injection plane.

3. A combustor for a gas dynamic laser as set forth in claim 1 wherein said first conduit means includes a first control valve means for controlling the oxidant therethrough, said second conduit means includes a second control valve means for controlling the fuel therethrough; and said third conduit means includes a third control valve means for controlling the diluent therethrough.

4. A combustor for a gas dynamic laser as set forth in claim 1 wherein O and N are injected through said first set of opening means, control valve means for varying the ratio of O to N being injected through said first set of opening means.

5. A combustor for a gas dynamic laser as set forth in claim 1 wherein said diluent for cooling and modifying the exhaust is N 6. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward end closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means for supplying a diluent from said diluent supply tank to said third conduit means; said combustion chamber is formed circular in cross-section and said second predetermined distance is approximately equal to the diameter of said combustion chamber.

7. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward end closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means for supplying a diluent from said diluent supply tank to said third conduit means; said combustion chamber is formed circular in cross-section and said third predetermined distance is approximately equal to two times the diameter of said combustion chamber.

8. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward end closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means for supplying a diluent from said diluent supply tank to said third conduit means; the fuel is CO with H added, the oxidant includes 0 the gas for cooling and modifying the exhaust includes N and the combustion chamber is formed circular in cross-section with the first and second predetermined distances being approximately equal to the diameter of said combustion chamber. 

1. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward end closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means f0r supplying a diluent from said diluent supply tank to said third conduit means; said combustion chamber is formed circular in cross-section and said first predetermined distance is approximately equal to the diameter of said combustion chamber.
 2. A combustor for a gas dynamic laser as set forth in claim 1 wherein the first set of opening means includes a plurality of first openings with a conduit having a smaller opening located concentrically in said first opening each conduit forming an annular opening with its cooperating first opening, each first opening and smaller opening of said conduits being directed to inject the fluids substantially radially inwardly along said first injection plane.
 3. A combustor for a gas dynamic laser as set forth in claim 1 wherein said first conduit means includes a first cOntrol valve means for controlling the oxidant therethrough, said second conduit means includes a second control valve means for controlling the fuel therethrough; and said third conduit means includes a third control valve means for controlling the diluent therethrough.
 4. A combustor for a gas dynamic laser as set forth in claim 1 wherein O2 and N2 are injected through said first set of opening means, control valve means for varying the ratio of O2 to N2 being injected through said first set of opening means.
 5. A combustor for a gas dynamic laser as set forth in claim 1 wherein said diluent for cooling and modifying the exhaust is N2.
 6. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward end closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means for supplying a diluent from said diluent supply tank to said third conduit means; said combustion chamber is formed circular in cross-section and said second predetermined distance is approximately equal to the diameter of said combustion chamber.
 7. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward end closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means for supplying a diluent from said diluent supply tank to said third conduit means; said combustion chamber is formed circular in cross-section and said third predetermined distance is approximately equal to two times the diameter of said combustion chamber.
 8. A combustor for a gas dynamic laser having an elongated combustion chamber with its forward enD closed and rearward end open; a first set of opening means located a first predetermined distance downstream of the front of said chamber for injecting a fuel and oxidant; a second set of opening means located a second predetermined distance downstream of said first set of opening means for injecting a diluent for cooling and modifying the exhaust to provide proper composition and temperature for a gas dynamic laser; a mixing chamber extends a third predetermined distance from the second set of opening means for obtaining even mixing of the exhaust; each of said opening means of said first set includes a first opening in the chamber and a second smaller opening located in said first opening; first conduit means extending outwardly from each of said first openings in the chamber; second conduit means extending outwardly from each of said smaller openings; an oxidant supply tank; means for supplying oxidant from said oxidant supply tank to said first conduit means; a fuel supply tank; means for supplying fuel from said fuel supply tank to said second conduit means; each of said opening means of said second set including a third opening in the chamber; third conduit means extending outwardly from said openings in the chamber; a diluent supply tank; means for supplying a diluent from said diluent supply tank to said third conduit means; the fuel is CO with H2 added, the oxidant includes O2, the gas for cooling and modifying the exhaust includes N2, and the combustion chamber is formed circular in cross-section with the first and second predetermined distances being approximately equal to the diameter of said combustion chamber. 